JP2001085201A - Ceramic composition for positive temperature coefficient thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a barium titanate positive temperature coefficient thermistor which is not deteriorated in breakdown voltage, allowable rush power, and on-off cycle life even when the specific resistance of an element material is reduced, and has a low resistance value. SOLUTION: A barium titanate solution expressed by a chemical formula, (BaxSryCazPdsDt)TiuO3, where x, y, z, s, t, and u respectively meet relations of 0.4180<=x<=0.8080, 0.02<=y<=0.030, 0.05<=z<=0.20, 0.01<=s<=0.15, 0.0010<=t<=0.0035, and 0.95<=u<=1.02, with x+y+z+s+t=1, and D represents at least one kind of rare-earth element of Pr or Sm, contains Mn and Si at rates of 0.001-0.0065 wt.% and 0.09-1.0 wt.%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a positive temperature coefficient thermistor porcelain composition.

[0002]

2. Description of the Related Art A barium titanate-based positive temperature coefficient thermistor is obtained by adding a rare earth element such as Y, La, or Ce to barium titanate as a main component to form a semiconductor, and has a low specific resistance at room temperature. Taking advantage of the property that the specific resistance rapidly increases when the Curie point is exceeded, it is widely used in degaussing circuits and overcurrent protection circuits of televisions. With the recent downsizing and cost reduction of electronic equipment, PTC thermistors are also required to have lower resistance, and in order to respond to this, it is necessary to lower the specific resistance of element materials. Various studies have been made in terms of composition and manufacturing process.

[0003]

In particular, in the case of a degaussing circuit, it has been studied to reduce the number of turns of the degaussing coil by reducing the resistance value of the element and increasing the inrush current, thereby reducing the cost. . In order to cope with this lowering of the resistance, the specific resistance of the element material to be used must be reduced from the conventional value of 40 Ω · cm or more to the range of 10 to 20 Ω · cm. However, when the specific resistance is reduced as described above, there is a disadvantage that the withstand voltage, the inrush allowable power, and the ON-OFF cycle life are reduced. Here, the withstand voltage is also referred to as a static withstand voltage, and means a maximum voltage that the element can withstand without being destroyed when a voltage is gradually applied to a positive temperature coefficient thermistor element (hereinafter, simply referred to as an element). The inrush allowable power is
The maximum voltage that the element can withstand without breaking when a voltage is instantaneously applied to the element. In particular, in the case of degaussing or motor starting, since voltage is repeatedly applied to the element, not only the withstand voltage performance but also the inrush allowable power is high and ON
-It is important that the OFF cycle life is long. As a method for improving the withstand voltage, Sr,
There is a method of containing Ca and Pb, which is already known (JP-A-57-157502). However, in this method, the specific resistance did not become lower than 35 Ω · cm, the inrush allowable power was low, and the ON-OFF cycle life was not sufficiently long. Further, a method for containing Y, Gd and Dy is also known, but in this method, the target of specific resistance is 10 to 10.
Although a range of 20 Ω · cm can be realized, the withstand voltage and inrush allowable power are low, and the ON-OFF cycle life is short. Therefore, the withstand voltage is improved and the specific resistance is 35Ω.
A porcelain composition capable of forming a positive temperature coefficient thermistor having a high permissible inrush power and a long ON-OFF cycle life of less than cm has been required.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems.
The composition formula (Ba_xSr_yCa_zPb
_sD _t) Ti_uO₃(X + y + z + s + t = 1)
The barium titanate-based solid solution has a composition value x
0.4180 ≦ x ≦ 0.8080, composition value y is 0.02
≦ y ≦ 0.30, composition value z is 0.05 ≦ z ≦ 0.20,
The composition value s is 0.01 ≦ s ≦ 0.15, and D is P
at least one of r and Sm, the composition value t of which is 0.00
10 ≦ t ≦ 0.0035, and the composition value u is 0.95 ≦
For the above composition formula where u ≦ 1.02, Mn is 0.0
01 wt% ≦ Mn ≦ 0.0065 wt%, Si is 0.0
By containing 9 wt% ≦ Si ≦ 1.0 wt%,
Withstand voltage, inrush allowable power and
And ON-OFF cycle life
A PTC thermistor with a low value was obtained. semiconductor
Y is commonly used as an agent, for the reason
Shows semiconductor conversion over a wider concentration range than other semiconducting agents.
That's why. In the present invention, barium titanate has Sr,
Various semiconducting agents were added to the system containing Ca and Pb.
The added composition was examined. As a result, 10-20Ωcm
When the specific resistance is lowered to the range, Y becomes withstand voltage and inrush allowable power.
The power was too low to reach a usable level. The above composition
(Ba_xSr_yCa_zPb_sD_t) Ti_uO₃(X + y
+ Z + s + t = 1), and 0.4180 ≦ x ≦ 0.808
0, 0.02 ≦ y ≦ 0.30, 0.05 ≦ z ≦ 0.2
0, 0.01 ≦ s ≦ 0.15, 0.0010 ≦ t ≦ 0.
0035, 0.95 ≦ u ≦ 1.02, semiconductor conversion
First by using Pr or Sm as agent D
Can be used satisfactorily even with a specific resistance in the range of 10-20Ωcm
Level withstand voltage, inrush allowable power and ON-OFF
The cycle life characteristics were obtained.

[0005]

According to the present invention, the composition formula (Ba _{x
Sr y Ca z Pb s D t} ) Ti u O 3 (x + y + z + s
+ T = 1), a composition value x is 0.4180 ≦ x ≦ 0.8080, a composition value y is 0.02 ≦ y ≦ 0.30, and a composition value z is 0.05. ≤
z ≦ 0.20, composition value s is 0.01 ≦ s ≦ 0.15, D is at least one of Pr and Sm, and the composition value t is 0.0010 ≦ t ≦ 0.0035, , Composition value u
Is 0.95 ≦ u ≦ 1.02,
Mn is 0.001 wt% ≦ Mn ≦ 0.0065 wt%,
Since the content of Si is 0.09 wt% ≦ Si ≦ 1.0 wt%, a positive temperature coefficient thermistor having a lower resistance than the conventional one without lowering the withstand voltage and the allowable rush power even if the specific resistance of the element material is lowered. Can be made.

[0006]

EXAMPLES BaCO ₃ , SrCO ₃ , CaC as raw materials
O ₃ , Pb ₃ O ₄ , TiO ₂ , Pr ₆ as a semiconducting agent
O ₁₁ , Sm ₂ O ₃ , MnCO ₃ , SiO as additives
₂ were prepared, and these were blended so as to have a predetermined composition shown in Tables 1 to 3. The mixture was wet-mixed, dehydrated and dried, and calcined at 1200 ° C. for 2 hours. Next, this was wet pulverized and then granulated by adding a binder to obtain a granulated powder. This is pressurized uniaxially to form a cylinder (diameter 18).
(mm, thickness 2.5 mm) and baked at 1300 ° C. for 1 hour to obtain a sintered element. An indium-gallium alloy was applied to both surfaces of the sintered element to prepare a sample for measuring the room temperature resistivity and the withstand voltage. Further, after forming electrodes (a two-layer electrode composed of a Ni electrode in the lower layer and a Sn electrode in the upper layer) on this sintered body element, a lead wire is connected, and measurement and ON of inrush allowable power are performed on the element covered with a covering resin. -An OFF cycle test (measurement of the number of cycles at which the element is broken) was performed. Further, a conventional example using Y as a semiconducting agent and Gd, D
The same test as described above was conducted for a comparative example using y. In Tables 1 to 3, A-1 to A-27 are examples according to the present invention, and a-1 to a-18 are comparative examples out of the claims of the present invention. Further, b-1 to b-6 are comparative examples using Gd and Dy as the semiconducting agents. Tables 1 to 3 show these results.

[0007]

[Table 1]

[0008]

[Table 2]

[0009]

[Table 3]

In the examples shown in Tables 1 to 3,
The mark indicates the characteristics required for the element material of the low-resistance positive temperature coefficient thermistor for demagnetization, that is, the specific resistance is less than 30 Ω · cm, the withstand voltage is 120 V / mm or more, the inrush allowable power is 260 V or more, and the ON-OFF cycle life is 30000 cycles or more. Is what you do. From Tables 1 to 3, Examples A-1 to A-27 of the present invention are all evaluated as ○, and the characteristics that can be used as the element material of the low-resistance demagnetizing positive temperature coefficient thermistor with lower resistance than the comparative example and the conventional example. It turns out that it is equipped with.

Here, the composition value x of Ba is 0.41
If it is less than 80, the specific resistance increases, and if it exceeds 0.8080, the withstand voltage and the inrush allowable power decrease. If the composition value y of Sr is less than 0.02, the withstand voltage decreases, and if it exceeds 0.30, the specific resistance increases. If the composition value z of Ca is less than 0.05, the withstand voltage decreases, and if it exceeds 0.20, the specific resistance increases. If the composition value s of Pb is less than 0.01, the withstand voltage decreases, and if it exceeds 0.15, the specific resistance increases. If the composition value t of the semiconductor element is less than 0.001, the electrical characteristics deteriorate, and if it exceeds 0.0035, the specific resistance increases. As described above, Pr and Sm
Can be used sufficiently even with a specific resistance in the range of 10 to 20 Ω · cm, inrush allowable power and ON-OFF.
Cycle life characteristics can be obtained. Further, although Y, Gd and Dy can realize the target range of the specific resistance of 10 to 20 Ω · cm, the withstand voltage and the inrush allowable power are low,
-Short OFF cycle life. The molar ratio u of Ti is 0.9
Except for 5 to 1.02, the specific resistance is high. If the added amount of Mn is less than 0.001 wt%, the electrical characteristics deteriorate,
When the content exceeds 0.0065 wt%, the specific resistance increases. Si
Is 0.09 wt% (0.2 wt% as SiO _2).
%), The sintering temperature is high, and the specific resistance is high under normal firing conditions, and good characteristics cannot be obtained. 1.0wt%
If it exceeds (2.1% by weight as SiO ₂ ), electrical characteristics deteriorate, and furthermore, the element is fused, which is a problem. Further, in the above example, Si was added as SiO ₂ , but the same effect could be obtained by adding it as Si ₃ N ₄ .

[0012]

Effects of the Invention composition formula _{(Ba x} Sr y _Ca z Pb
_{s D t) Ti u O 3} (x + y + z + s + t = 1) in barium titanate based solid solution represented by the composition value x is 0.4180 ≦ x ≦ 0.8080, the composition value y is 0.02
≦ y ≦ 0.30, composition value z is 0.05 ≦ z ≦ 0.20,
The composition value s is 0.01 ≦ s ≦ 0.15, and D is P
at least one of r and Sm, the composition value t of which is 0.00
10 ≦ t ≦ 0.0035, and the composition value u is 0.95 ≦
For the above composition formula where u ≦ 1.02, Mn is 0.0
01 wt% ≦ Mn ≦ 0.0065 wt%, Si is 0.0
By containing 9 wt% ≦ Si ≦ 1.0 wt%,
Even if the element material is made to have a low specific resistance, a positive temperature coefficient thermistor having a low resistance value can be obtained without lowering the withstand voltage, allowable rush power and ON-OFF cycle life. Therefore, the present invention can be applied to a positive temperature coefficient thermistor for various uses including an element material of a demagnetization positive temperature coefficient thermistor having a lower resistance than the conventional one, and its industrial value is great.

[Procedure amendment]

[Submission date] March 8, 2000 (200.3.8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art A barium titanate-based positive temperature coefficient thermistor is obtained by adding a rare earth element such as Y or La to barium titanate as a main component to form a semiconductor, and has a low specific resistance at room temperature but a Curie point. It is widely used in degaussing circuits, overcurrent protection circuits and the like of televisions, taking advantage of the property that the specific resistance suddenly increases when it exceeds. With the recent downsizing and cost reduction of electronic equipment, PTC thermistors are also required to have lower resistance, and in order to respond to this, it is necessary to lower the specific resistance of element materials. Various studies have been made in terms of composition and manufacturing process.

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Claims (1)

[Claims] 1. A composition formula _{(Ba x} Sr y _Ca z Pb
_{s D t) Ti u O 3} (x + y + z + s + t = 1 in the barium titanate-based solid solution represented by), the composition value x .4180 ≦ x ≦ .8080, composition value y
Is 0.02 ≦ y ≦ 0.30, and the composition value z is 0.05 ≦ z ≦
0.20, the composition value s is 0.01 ≦ s ≦ 0.15, and D is at least one of Pr and Sm, and the composition value t
Is 0.0010 ≦ t ≦ 0.0035, and Mn is 0.001 wt% ≦ Mn ≦ 0.0065 wt% with respect to the above composition formula in which the composition value u is 0.95 ≦ u ≦ 1.02.
A positive temperature coefficient thermistor porcelain composition characterized in that Si is contained in an amount of 0.09 wt% ≦ Si ≦ 1.0 wt%.